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Merge_Sort.cpp
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Merge_Sort.cpp
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/*MERGE SORT*/
#include<iostream>
using namespace std;
long long int s;
long long int mergesort(long long int *left,long long int leftsize,long long int *right,long long int rightsize,long long int *A)
{
long long int i=0;
long long int j=0;
long long int k=0;
while(i<leftsize && j<rightsize)
{
if((*(left+i))<(*(right+j)))
{
*(A+(k++))=*(left+(i++));
}
else
{
s+=(leftsize-i);
*(A+(k++))=*(right+(j++));
}
}
while(i<leftsize)
{
*(A+(k++))=*(left+(i++));
}
while(j<rightsize)
{
*(A+(k++))=*(right+(j++));
}
}
void merge(long long int *A,long long int n)
{
long long int *left,*right,i,j;
//cout<<n<<endl;
if(n<2)
return;
else
{
long long int mid=(n/2);
left=new long long int[mid];
right=new long long int[n-mid];
for(i=0;i<mid;i++)
*(left+i)=*(A+i); //Size of left array :mid
for(j=0;j<(n-mid);j++) //Size of right array:(n-mid)
*(right+j)=*(A+(j+mid));
merge(left,mid);
merge(right,(n-mid));
mergesort(left,mid,right,(n-mid),A);
}
}
int main()
{
long long int n,i,t;
// cout<<"Enter the size of array";
cin>>t;
while(t--)
{
s=0;
cin>>n;
long long int *a;
a=new long long int[n];
for(i=0;i<n;i++)
cin>>(*(a+i));
merge(a,n);
cout<<s<<endl;
}
}